1. Field of the Invention
The invention relates to the care of hoof cracks in hooved animals.
2. Brief Description of the Prior Art
Hooved animals such as cows, horses and the like are susceptible to many diseases and injuries related to defects in their hooves. For example, the hoof of the horse is subject to quarter cracks, heel cracks and toe cracks. The location of the crack is what designates its name.
The horse hoof (ungula) is the cornified epidermis of the animal's foot, comprised of a wall, sole and frog. It is non-vascular and lacks nerve endings. The wall is structured of keratinized epithelial cells, solidly cemented with keratin a scleroprotein rich in sulfur containing amino acid residues. The hoof wall, which overlies the more sensitive lamellar corium tissue of the foot, contains about 25 percent water and small amounts of minerals such as calcium, magnesium, zinc, copper and manganese making it a relatively dense material.
The hoof wall (paries) is composed of three layers, the outer layer being the periople and the stratum tectorium which gives the wall its glossy appearance and protects the hoof from dehydration. Underlying the stratum tectorium is the middle layer, which is the densest portion of the hoof wall and overlies the epidermal laminae or inner layer.
The ground surface of the hoof is arbitrarily divided into the toe, quarter or heel zones referred to above, and so referred to in designating the location of hoof cracks.
The most common causes of hoof cracks are trauma, infection of the underlying sensitive laminae, poor hoof and leg conformation, poor trimming or shoeing and invasion of the white line (the juncture of the hoof wall and the sole), by bacteria, fungus or mold. Other causes can be attributed to drying or excessively thin walls or injury to the coronary band. Once the crack occurs, the natural expansion and contraction of the hoof, due to the loading and unloading of the foot in motion, causes the hoof wall to pinch and irritate the underlying sensitive laminae within the hoof capsule. Lameness may not occur immediately but inevitably ensues.
Over the years, this problem has been handled several ways, depending on location of the crack.
In one common expedient, metal plates have been placed across the cracks and fastened to the hoof wall with sheet metal screws. This does not pull the crack together but does stabilize it until the screws loosen due to concussion or normal hoof growth. It also makes it possible for the underlying sensitive laminae to be invaded when drilling the holes for the screws thus causing the hoof to abscess, further exacerbating the problem.
The preferred treatment for toe cracks which do not extend into the coronary band has comprised burning or grooving a triangular pattern in the hoof surface across the upper reaches of the crack, with the apex of the triangle sitting on a groove or burn transverse to the crack. This is to limit extension of the crack. The hoof wall is then trimmed away on either side of the crack at the ground surface. A shoe is then applied to the hoof to remove weight bearing at the toe site of the crack. The area between the shoe and the injury site must be cleaned daily (usually with a hacksaw blade) to avoid injury. Eventually, and after a number of re-shoeings, the hoof grows out, eliminating the crack (the hoof wall grows downward at a rate of about one-fourth inch per month, depending on temperature and humidity of the environment.
Quarter cracks have been similarly treated, but with installation of half-bar shoes with the bar on the heel of the affected side pressing with 1/8 to 1/4 inch of pressure upon the frog. This relieves pressure on the hoof wall at the site of injury. Daily cleaning of the clipped site between the shoe and the injury site are likewise mandatory to avoid infection. Heel cracks, similarly treated usually do not require special shoeing.
Cracks have also been stitched together with wire, again opening the possibility of penetrating into the underlying sensitive laminae when drilling holes on either side of the crack to allow for the passing of the wires across the crack. When the wires are pulled or twisted in an effort to close or stabilize the crack they invariably pull through the fibers of the hoof wall and are ineffective, even causing greater injury.
Recently, glue-on patches have been introduced but leave much to be desired. Often the glue fails if the area is not prepared "correctly" which, under most conditions, is near impossible. Since the patches are a plastic material, they are subject to movement and cannot be used to pull the crack together.
A state-of-the-art treatment for treating toe and quarter cracks in horse hooves has been more complex. The crack is debrided with an electric cast cutter, a hoof groover, a firing iron or a motorized burr to enlarge it down to the sensitive laminae. The opening is made triangular, with the base of the triangle at the layer of the sensitive laminae. Holes are drilled on both sides of and parallel to the crack. The holes are threaded with umbilical tape or stainless steel wire. Then, the crack is filled with epoxy glue or a like plastic and the crack reduced by pulling and tensioning the tape or wire like a shoelace. Corrective shoes as described above are also applied to reduce the ground-to-hoof pressure on the site of injury. The procedure, described by Evans et al. in JAVMA, Vol. 148 [1966] at Page 355 is not without hazards. One problem is that the heat generated by the epoxy glue curing (or most plastic adhesives) can destroy tissue beneath it, resulting in abscess formation.
In actual use on horses with cracks that were chronic and long standing, the assembly of the present invention has overcome all the problems mentioned above. While other remedies proved ineffective, the assembly of the invention eliminated expansion and contraction of the crack so that the soreness and inflammation to the underlying sensitive laminae were gone in a matter of days and the horses were sound in a short time.
In cases where the sensitive laminae had been irritated to the extent that there was an infection, the crack was debrided and treated with antiseptics, packed with cotton and the assembly of the invention was put in place. This allowed the crack to be treated daily since the cotton was exposed and could be saturated with antiseptics and the wound could drain. This was also the case with cracks that had been invaded by fungus or mold. In all cases the cracks, after several shoeings, had grown down and normal hoof growth, which starts at the hair line, had begun and the hoof had returned to its normal state.